Leaf physiological versus morphological acclimation to high-light exposure at different stages of foliar development in oak
J. Rodríguez-Calcerrada (1), P. B. Reich (2), E. Rosenqvist (3), J. A. Pardos (1), F. J. Cano (1) and I. Aranda (4, 5)
1. Unidad de Anatomía, Fisiología y Genética Forestal, Escuela Técnica Superior de Ingenieros de Montes, Universidad Politécnica
de Madrid (UPM), Ciudad Universitaria s/n, E-28040, Madrid, Spain / 2. Department of Forest Resources, University of Minnesota, St. Paul, MN 55108, USA / 3. Department of Agricultural Science, University of Copenhagen, Hojbakkegaard Allé 21, DK-2630 Taastrup, Denmark / 4. Centro Nacional de Investigación Forestal (CIFOR), Instituto Nacional de Investigación Agraria y Alimentaria (INIA), Apdo.
8111, E-28080, Madrid, Spain / 5. Corresponding author () / Received June 18, 2007; accepted September 18, 2007; published online March 3, 2008
Summary
We investigated light acclimation in seedlings of the temperate oak Quercus petraea (Matt.) Liebl. and the co-occurring sub-Mediterranean oak Quercus pyrenaica Willd. Seedlings were raised in a greenhouse for 1 year in either 70 (HL) or 5.3% (LL) of ambient irradiance of full sunlight,
and, in the following year, subsets of the LL-grown seedlings were transferred to HL either before leaf flushing (LL-HLBF
plants) or after full leaf expansion (LL-HLAF plants). Gas exchange, chlorophyll a fluorescence, nitrogen fractions in photosynthetic
components and leaf anatomy were examined in leaves of all seedlings 5 months after plants were moved from LL to HL. Differences
between species in the acclimation of LL-grown plants to HL were minor. For LL-grown plants in HL, area-based photosynthetic
capacity, maximum rate of carboxylation, maximum rate of electron transport and the effective photochemical quantum yield
of photosystem II were comparable to those for plants grown solely in HL. A rapid change in nitrogen distribution among photosynthetic
components was observed in LL-HLAF plants, which had the highest photosynthetic nitrogen-use efficiency. Increases in mesophyll
thickness and dry mass per unit area governed leaf acclimation in LL-HLBF plants, which tended to have less nitrogen in photosynthetic
components and a lower assimilation potential per unit of leaf mass or nitrogen than LL-HLAF plants. The data indicate that
the phenological state of seedlings modified the acclimatory response of leaf attributes to increased irradiance. Morphological
adaptation of leaves of LL-HLBF plants enhanced photosynthetic capacity per unit leaf area, but not per unit leaf dry mass,
whereas substantial redistribution of nitrogen among photosynthetic components in leaves of LL-HLAF plants enhanced both mass-
and area-based photosynthetic capacity.
